nfsd: fix crash on COPY_NOTIFY with special stateid

RTM says "If the special ONE stateid is passed to
nfs4_preprocess_stateid_op(), it returns status=0 but does not set
*cstid. nfsd4_copy_notify() depends on stid being set if status=0, and
thus can crash if the client sends the right COPY_NOTIFY RPC."

RFC 7862 says "The cna_src_stateid MUST refer to either open or locking
states provided earlier by the server.  If it is invalid, then the
operation MUST fail."

The RFC doesn't specify an error, and the choice doesn't matter much as
this is clearly illegal client behavior, but bad_stateid seems
reasonable.

Simplest is just to guarantee that nfs4_preprocess_stateid_op, called
with non-NULL cstid, errors out if it can't return a stateid.

Reported-by: [email protected]
Fixes: 624322f1adc5 ("NFSD add COPY_NOTIFY operation")
Signed-off-by: J. Bruce Fields <[email protected]>
Signed-off-by: Chuck Lever <[email protected]>
Reviewed-by: Olga Kornievskaia <[email protected]>
Tested-by: Olga Kornievskaia <[email protected]>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index eb920f855969..72900b89cf84 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -6058,7 +6058,11 @@ nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
 		*nfp = NULL;
 
 	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid)) {
-		status = check_special_stateids(net, fhp, stateid, flags);
+		if (cstid)
+			status = nfserr_bad_stateid;
+		else
+			status = check_special_stateids(net, fhp, stateid,
+									flags);
 		goto done;
 	}